The invention relates to an apparatus for inspecting the underside of bridges, with an undercarriage, an intermediate carrier attached to the undercarriage, a guide member mounted on the intermediate carrier rotatably about a horizontal axis of rotation, a lifting tower received by the guide member, movable perpendicularly relative to its axis of rotation and having four corner spars, a lifting-tower bottom part mounted on the lifting tower rotatably about its longitudinal mid-axis, and a work platform attached to the lifting-tower bottom part.
In known apparatuses of this type for inspecting the underside of bridges, the lifting tower has a symmetrical, especially square cross-section, and the guide member encloses it all round. Such a guide member of hollow cross-section which receives the tower cross-section, is also designated as a guide box. Disadvantages are the large amount of space required, which makes it difficult to fold the apparatus together compactly for transport, and the unfavorable weight distribution as a result of the symmetrical cross-section of the lifting tower.